1. Field of the Invention
This invention relates to a data recording medium for which digital data is recorded or reproduced with a laser beam, and more particularly to a data recording medium suitable for an optical disk for recording and reproducing digital data. This invention further relates to an apparatus and method for recording or reproducing digital data for such a data recording medium.
2. Description of the Prior Art
Various kinds of optical disks have been developed in recent years as digital recording media for recording and reproducing large volumes of data. One of these is the DVD-ROM that employs 8-16 modulation.
The 8-16 modulation adopted in the DVD-ROM converts an 8-bit data symbol to a 16-bit code word. A plurality of code words corresponds to one data symbol. Which one of the code words is selected is decided with reference to a DSV (Digital Sum Value) and state information designated for each code word. The DSV is obtained by adding +1 for a positive side and xe2x88x921 for a negative side of the NRZI converted signal of a modulated code. The DSV determined for each code word is called a CDS (Code Word Digital Sum). The code word is selected with reference to the DSV for the code word after the code word to be currently selected. The DSV is calculated cumulatively from the first data symbol to the data symbol just before the data symbol to be converted currently and is referenced to select the code word. Demodulation is performed by converting the 16 bits of the current code word into an 8-bit data symbol with reference to the 2bits of the state information bits of the next code word.
FIG. 12 shows a sector format employed in DVD-ROM. In FIG. 12, a data area 14y is an area in which data is recorded and a sync area 14x is an area including synchronization information to be used for reading out data from the data area 14y. A pair of the sync area 14x and the data area 14y composes a frame, and 26 frames compose one sector. The sync area 14x and the data area 14y are formed continually.
In this format, the latest data symbol recorded on the data area is demodulated with reference to the state information bits included in sync area immediately after that data area.
Now, for a DVD which is capable of recording, the aforementioned format is not applied. Such a DVD needs some other areas, for example, an area for sector identification and an area for laser power calibration for data recording, in addition to the area on which data is recorded (the sync area and data area). Therefore, the area on which data is recorded is not continuous in every sector, and the final data area in the sector is not followed by the sync area. Accordingly, the state information required for demodulation of the final code word in the last data area of the sector cannot be obtained.
Therefore, A conventional apparatus for reproducing data from a DVD with the conventional format shown in FIG. 12 cannot reproduce data from a DVD with the format capable of recording described above.
An object of the present invention, which is devised for the purpose of resolving the problems stated above, is to provide a data recording medium capable of recording digital data, and more particularly a data recording medium suitable for an optical disk.
A further object of the present invention is to provide an apparatus and a method for data recording or reproducing with the data recording medium.
In a first aspect of the invention, a data recording medium having a region for recording data is provided. The region has a plurality of sectors. Each sector comprises a recording area and a postamble area. The data recording area stores a plurality of modulated codes obtained by modulating the data. The postamble area is located immediately after the data recording area and stores a data pattern which includes synchronization information to be used for synchronizing. The data pattern in the postamble area may be determined from a predetermined plurality of patterns based on a DSV calculated for the pattern accompanied with data stored in the recording area so that DSV becomes smaller. The data pattern may also be determined to satisfy a run length limitation. The data pattern in the postamble area may also include information to demodulate the final modulated code in the data area.
In a second aspect of the invention, an apparatus is provided for recording data in the form of modulated data to a data recording medium. The data recording medium has a region for recording data. The region has a plurality of sectors. Each sector includes a data recording area to store modulated codes obtained by modulating the data. The data recording apparatus comprises a pattern generator and a recording unit. The pattern generator generates at least one data pattern including a synchronization pattern to be used for synchronizing. The data pattern may also include information to demodulate the final modulated code stored in the data recording area. The data pattern may be determined from a predetermined plurality of patterns based on a DSV calculated for the pattern so that DSV becomes smaller. The data pattern may be determined to satisfy a run length limitation. The recording unit records one of the data patterns from the pattern generator in the area immediately after the data recording area.
In a third aspect of the invention, an apparatus is provided for reproducing data from a data recording medium. The data recording medium has a region for recording data. The region has a plurality of sectors. Each of the sectors includes a data recording area and a postamble area located immediately after the data recording area. The data recording area includes a sync area storing a synchronization pattern to be used for synchronizing and a data area storing modulated data obtained by modulating the data. The postamble area stores a data pattern including a part of the synchronization pattern. The data reproducing apparatus comprises a reproducing unit, an area detector and a demodulator. The reproducing unit reads out data from the recording medium in the form of an analog modulated signal, and converts the analog modulated signal into digital data. The area detector detects the sync area and the data area based on the digital data, and generates a predetermined control signal while the sync area and the data area are detected. The demodulator demodulates the digital data from the reproducing unit while the area detector generates the control signal.
In a fourth aspect of the invention, a method is provided for recording data in the form of modulated codes to a data recording medium. The data recording medium has a region to record data. The region has a plurality of sectors. Each of the sectors includes a data recording area to store the modulated codes obtained by modulating the data. The data recording method comprises generating at least one data pattern including at least a part of synchronization pattern to be used for synchronizing, and recording one of the generated data patterns in the area immediately after the data recording area.
In a fifth aspect of the invention, a method is provided for reproducing data from a data recording medium. The data recording medium has a region for recording data. The region has a plurality of sectors. Each of the sectors includes a data recording area and a postamble area located immediately after the data recording area. The data recording area includes a sync area storing a synchronization pattern to be used for synchronizing and a data area storing modulated data obtained by modulating the data. The postamble area stores a data pattern including a part of the synchronization pattern. The data reproducing method comprises reading out data from the recording medium in the form of analog modulated signal, converting the analog modulated signal into digital data, detecting the sync area and the data area based on the digital data, generating a predetermined control signal while the sync area and the data area are detected, and demodulating the digital data while the control signal is being generated.